Method of cementation of boron into the surface of iron or steel



Patented Nov. 1923.

TAKEO MIYAGUCHI, OF SENDAGAYAMACHI, TOYOTAMAGORI, TOKYOFU, JAPAN.

METHOD OF CEMENTATION OF BORON INTO THE SURFACE OF IRQN OR STEEL.

No Drawing.

tion.

My invention relates to improved method of cementation of boron into any desired surface of iron or steel and has for its object the obtainin of tough and hard surface of the metal w iich is to be utilized in making articles of excellent quality such as bolt heads, knife blades, razor blades, chiselsor the like. The further object of the invention is to minimize the wear and tear of the friction surface of shafts, gear wheels, ballhearings or the like.

This invention is an improvement on the method of my copending application Serial No. 508,819 and is also an improvement on the British Patent No. 19461, A. D. 1912. I made exhaustive tests with a View toarriving at an effective and simple method of cementation of boron into the surface of iron or steel.

I have attempted to obtain desired cementation of boron as described in the above British patent by the employment of carburizing substance such as carbon powder and boron oxide or ferro-boron in an ordinary atmosphere, but I have failed in this way and at last I have succeeded by carrying out the treatment within reducing at mosphere.

In my invention, first, clean the desired surface of iron or steel, then cover the portion where the boron is to be cemented with a mixture of carbon powder and bpron oxide, or of carbon powder and boron com-' pound such as borax. The remaining portion is to be shielded with clay or the like in order to prevent the action of boron. Then heat the iron or steel in a furnace up to about 800 or 900 C. in a reducing atmosphere such as provided by gases containing a sufiicient quantity of carbon monoxide. The boron in the boron oxide or boron comound becomesreduced by carbon powder with the aid of the reducing atmosphere and the reduced boron penetrates into the surface of the iron or steel to a. certain depth.

Application filed October 19, 1921. Serial No. 508,817.

According to my tests,- the cementation of boron and chromium into the. surface of iron or steel by diffusion as described in the above British patent was shown as a mere trace and can not afford any beneficial effect to be adapted for commercial use.

On the other hand, in my process such cementation of boron into the surface of ironor steel can be secured so as to meet commercial requirements, so that the product thus obtained possesses appreciable characteristics of boron cementation. But the cement-ation is not so deep as in my copending application although it gives decidedly distinctstructure of boron in the surface by microscopic inspection.

This method can be accomplished likewise -on the surface of special metals such as metals containing chromium, silicon, nickel, pilgfiganese, tungsten, molybdenum or the What I- claim 1. A method of cementation of boron into the surface of-iron or steel comprising covering the desired surface of the iron or steel witha mixture of carbon powder and boron oxide or compound, and heating it at from 800 C. to 900 C. in a reducing atmosphere.

2. A method of cementation of boron into the surface'of iron or steel comprising covering the desired surface of the iron or'steel with ferro boron, and heating it at from 800 C. to 900 C. in areducing atmosphere.

3. A method of cementation of boron into the surface of ferrous alloys comprising, covering the surface of the alloy to be treated with a mixture of carbon powder and boron oxide or compound, and heating it at from 800 C. to 900 .C. in a reducing. atmosphere.

4. A method of cementation of boron into the surface of ferrous alloys comprising, covering the surface of. the alloy to be treated with ferro-boron, and heating it at from 800 C. to 900 C. in a reducing atmosphere. 

